Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
1999-12-15
2002-04-02
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S448000, C428S215000, C428S323000, C399S320000, C399S329000, C399S333000
Reexamination Certificate
active
06365279
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a member that can be used as a fusing roller for hot pressure fixing of toner particles or as an intermediate member in transfuse systems. It relates in particular to such a roller with specified elastomeric layers, in particular silicone rubbers.
BACKGROUND OF THE INVENTION
In electro(photo)graphic copiers or printers, the toner image formed on the photoconductor can be transferred directly to the final image receiver, e.g. plain paper whereon it is fixed by fusing the toner particles by heat and pressure using fixing rollers. The toner image formed on the photoconductor or brought on a means for collecting the colour separations when performing colour printing, can be transferred not directly to the final image receiving member but in a first transfer zone to an intermediate member that can be heated and from that intermediate member to the final image receiving member whereon it is fixed by the heating of the intermediate member that is pressed against the final image receiving member by a pressure means. This latter process is further on termed as a “transfuse” and the intermediate member is designated by “transfusing member”.
Fusing and fixing of toner particles to a substrate by simultaneous application of heat and pressure are well known in the art and also fusing rollers for use in hot pressure fixing of toner particles are well known.
In, e.g., U.S. Pat. No. 4,078,286 a fusing roller is disclosed with a base member and thereon a first layer of an heat resistant resin and on top of the first layer a layer of silicone rubber.
In U.S. Pat. No. 4,257,699 and its equivalent EP-A
—
018 140 a fuser member with a base material and two elastomer layers thereon, the outer elastomer layer containing a metal filler is disclosed. In U.S. Pat. No. 5,049,444 a multi-layered fusing member is disclosed. This member has in sequential order a base support member, an adhesive layer, a tie coat layer and an outer elastomeric fusing layer with therein a copolymer with vinylidene fluoride and a metal oxide.
Also transfusing members are well known in the art. When transfusing members are in contact with the photoconductor it is important that the photoconductor is not soiled by impurities present in the final imaging member. Therefore transfusing members comprising two layers, a top layer permeable for the impurities and a layer under the top layer absorbing the impurities have been disclosed. In, e.g., EP-A-146 980 a transfusing member is described consisting of a metal roller provided with a first covering of pigmented RTV silicone rubber (RTV201/200, wherein silica particles are present) and a second covering of non-pigmented silicone rubber obtained by cross-linking an &agr;,&ohgr;-hydroxy-polymethylsiloxane with a tetra-ethyl silicate under influence of di-butyl tin dilaurate.
In EP-A-581 365 a transfusing member is disclosed consisting of a support with a pigmented rubber layer, wherein the pigment is preferably carbon black, and a top layer of silicone rubber.
In most of the applications of both a fusing roller and a transfusing member, a release agent, most frequently a silicone oil, is applied to the fusing or transfusing members to prevent hot-offset (i.e. toner particles adhering to the surface of the fusing or transfusing members instead of to the substrate) and to enhance the lifetime of the surface of the fusing and transfusing members.
The use of a release agent can however create problems in the finished image, basically because it gives kind of gloss to the image and that, when the release agent is not evenly spread over the image differences in gloss appear. Thus the use of release agents frequently entails problems of streaks, oily look, patchiness, etc. in the finished image. When silicone oil is applied to a transfusing member that comes in direct contact with the photoconductor, the photoconductor can be soiled by the silicone oil and therefore it is important that the use external release agent can be minimised or preferably avoided.
It has been proposed, for avoiding hot-offset when using a low amount of release agent, to change the properties of the toner particles, especially the type of toner resin that is used. Such toner particles have been disclosed in, e.g., EP-A-712 881 and EP-A-740 217. These measures do indeed offer the possibility of hot-pressure fixing even when using very low amounts of release agent, but because of the need to use special toner resins, the degrees of freedom in toner design, e.g., with respect to mechanical strength, chargeability, etc., are diminished.
Therefore the need for fusing and/or transfusing members that can be used, when only small amounts of release agent is used, is still there.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of this invention to provide a fusing member that can be used in hot-pressure fixing of toner particles to a substrate while avoiding the use of substantial amounts of release agents on the surface of the fusing member.
It is a further object of the invention to provide a fusing member that can be used in hot-pressure fixing of toner particles to a substrate while avoiding the use of substantial amounts of release agents on the surface of the fusing member that can be for a very long time preparing a large amount of prints before hot-offset appears.
It is an other object of the invention to provide a method for hot-pressure fixing of toner particles wherein only small amounts of release agent are applied to the fusing roller.
Further objects and advantages of the invention will become clear from the detailed description hereinafter.
The objects of the invention are realised by providing a fusing member comprising a support, and on said support,
an outermost layer containing a silicone elastomer, with at most 5% by weight of filler particles, said elastomer layer having a swelling factor, SF, equal to or higher than 3 and a thickness between 5 and 500 &mgr;m, both limits included and
a second layer with an impurity absorbing material, closer to said support and immediately in contact with said outermost layer, said second layer being at least 40 &mgr;m thick. Preferably said second layer has silicone containing elastomer and contains at least 5% by weight of metal oxide particles having a specific surface of ≧30 m
2
.
The objects of the invention are further realised by providing an imaging method comprising the steps of:
image-wise applying toner particles to a substrate and
fixing said toner particles to said substrate by simultaneous application of heat and pressure, characterised in that:
said fixing proceeds in a fusing system wherein a fusing member is present comprising
a support, and on said support,
an outermost layer containing a silicone elastomer, with at most 5% by weight of filler particles, said elastomer layer having a swelling factor, SF, equal to or higher than 3 and a thickness between 5 and 500 &mgr;m, both limits included and
a second layer with an impurity absorbing material, closer to said support and immediately in contact with said outermost layer, said second layer being at least 40 &mgr;m thick and
that at most 320 mg/m
2
of a release agent is applied to the surface of said fusing roller.
DETAILED DESCRIPTION OF THE INVENTION
As described above, during fusing and transfusing a release agent, most frequently a silicone oil, is applied to the fusing or transfusing members to prevent hot-offset (i.e. toner particles adhering to the surface of the members instead of to the substrate) and to enhance the lifetime of the surface of the fusing and transfusing members. In this document the wording “fusing member” will be used to indicate both a fusing member and a transfusing member. It was now found, after experimentation, that it was possible to design a member that could be used as fusing member with a very low amount of external release agent, e.g. silicone oil, or even without any external release agent and still had a long lifetime and did not show hot-offset. Therefore the fusing member, as in the prior art, comprised two
De Meutter Stefaan
Tavernier Serge
Van Wunsel Danny
Dawson Robert
Feely Michael J
Knobbe Martens Olson & Bear LLP
Xeikon N.V.
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